1. Field of the Invention
The present invention relates to a power supply abnormality detection circuit for an on-vehicle electronic control device, for reducing an abnormality of a feed circuit, and particularly, a trouble caused due to contact failure of a power supply terminal of a connector for connection in, for example, an engine control device fed with power from an on-vehicle battery through an output contact of a power supply relay.
2. Description of the Related Art
In an on-vehicle electronic control device fed with power from an on-vehicle battery through an output contact of a power supply relay, when an operation of the on-vehicle electronic control device is abnormal, it is important to determine whether or not a normal power supply voltage is applied in order to facilitate a maintenance check.
However, for example, while the on-vehicle electronic control device is not fed with power because of the abnormality of the power supply relay, it is difficult to determine and store an abnormal state in the on-vehicle electronic control device with no power being fed.
Therefore, there are conventional technologies with the following structures (see, for example, JP 2003-191804 A, JP 08-114530 A, JP 09-119889 A, and JP 08-198038 A). In a vehicle communication system described in JP 2003-191804 A, communication means for communicating data through communication lines wired in a vehicle are provided in a plurality of electrical devices mounted on the vehicle, whereby data can be transmitted and received among the respective electrical devices. A plurality of communication means for communicating the same data using different communication lines and selection means for selecting normal reception data from a plurality of items of reception data obtained by communication using the plurality of communication means are provided in each of the electrical devices. Provided as the electrical device is a power supply monitor device for monitoring a power supply state from an on-vehicle power source to an on-vehicle device including the respective electrical devices and transmitting a result obtained by monitoring to other electrical devices through the plurality of communication means including low-speed communication means, which is a feature of the vehicle communication system.
A power supply failure detection device described in JP 08-114530 A includes: a first power supply circuit for supplying power from an on-vehicle power supply to an on-vehicle electrical load including an on-vehicle electronic control unit through a key switch; voltage drop detecting means for detecting a voltage drop of the first power supply circuit and outputting a result obtained by detection to the on-vehicle electronic control unit; abnormality determining means which is provided in the on-vehicle electronic control unit, for determining an abnormality of the first power supply circuit based on an output of the voltage drop detecting means; abnormality handling means which is provided in the on-vehicle electronic control unit, for storing abnormality information based on a determination result obtained by the abnormality determining means or operating an abnormality display device; and a second power supply circuit for supplying operating power to the on-vehicle electronic control unit at the time of the voltage drop of the first power supply circuit.
An abnormality warning device for a vehicle which is described in JP 09-119889 A includes abnormality diagnosing means for diagnosing the presence or absence of an abnormality of a specific region of a vehicle. In the abnormality warning device for a vehicle, when the abnormality is detected by the abnormality diagnosing means, warning display means is driven by a driving circuit to display a warning. A feature of the abnormality warning device is to have wiring which is formed such that driving power to be supplied to the driver circuit of the warning display means is supplied through the warning display means. With this feature, for example, even when an abnormality of a power supply system for an engine control device occurs, a warning can be displayed.
A back-up power supply device for a vehicular electronic control unit which is described in JP 08-198038 A includes: a first power supply line connected between a battery and a microprocessor of the vehicular electronic control unit through a key switch; a second power supply line connected directly between the battery and the control unit without through the key switch; a load connected with the battery through the key switch; comparator means for comparing a voltage of the first power supply line with a voltage supplied to the load and generating a trigger output when the former is lower than the latter; and switch means operated to be closed in response to the trigger output to make electrical connection between the first power supply line and the second power supply line.
However, the conventional technologies have the following problems.
According to the vehicle communication system described in JP 2003-191804 A, when a power supply is not supplied to any of the large number of electrical devices which are illustrated, an abnormal state can be reported to other electrical devices or an abnormality can be indicated by a display device.
However, when contact failure of a connector to be connected with an electrical device causes the abnormality regardless of the normal operation of a power supply relay (not shown), there is a problem in that the cause of the abnormality cannot be identified. In addition, there is a problem in that the electrical device itself cannot determine the abnormality, report the abnormality, or store abnormality occurrence information.
In the power supply failure detection device described in JP 08-114530 A, two power supply relays are used to selectively switch between power feed circuits, and one of the power supply relays which causes an abnormality due to instantaneous power interruption is replaced by the other power supply relay, whereby the electronic control unit is fed with power through the other power supply relay. An anti-instantaneous power interruption circuit including the pair of power supply relays is provided outside the electronic control unit.
The electronic control unit is generally housed in a sealed case including high-density contactless electronic parts, and thus electromagnetic relays which are consumable parts causing contact arc cannot be incorporated. Therefore, when the contact failure of the connector to be connected with the electronic control unit causes the abnormality, there is a problem in that the cause of the abnormality cannot be identified. In addition, there is a problem in that the electronic control unit itself cannot determine the abnormality, report the abnormality, or store the abnormality occurrence information.
According to the abnormality warning device for a vehicle which is described in JP 09-119889 A, when an output contact of a power supply relay causes contact failure, the abnormality can be indicated by the warning lamp. However, the abnormality occurrence information cannot be stored. In addition, there is a problem in that whether the output contact causes the contact failure or a power supply terminal of the connector causes the contact failure cannot be determined.
The back-up power supply device for a vehicular electronic control unit which is described in JP 08-198038 A requires power transistors serving as a back-up power supply, which may cause increases in size and cost.